Unfortunately there is only a small window in my kids room. The decor looks lifeless without proper lighting. I had consulted TBS gallery regarding this. They said they can install some window treatments that can make the room look spacious and brighter. Can anyone share their opinion, can anything be done besides window treatment?

Painting the wall a brighter color would be a great way to brighten it up. If adding a larger window isn't in your budget, consider adding some soft lights around the room. If you use soft lamps with bulbs that aren't too intense, you can possibly re-create to feel of natural light.